HuBER, Innefvation of the Intracranial Vessels. 19 



pressing the brain tissue out from under the pia) it is often impos- 

 sible to differentiate between the small arterial branches in the 

 pia-mater and those which penetrate the brain substance — intra- 

 cerebral branches. As previously stated, small vessels with two 

 to three layers of involuntary muscle cells in the media possess 

 vaso-motor nerves. Whether some of these arterioles were intra- 

 cerebral, I can not say ; it seems however very probable, as 

 such vessels correspond in size and structure of coats to many 

 of the intra-cerebral arterioles found in the cortex. Kolliker (6) 

 states that he was able to trace perivascular nerves into the sub- 

 stance of the brain. 



I have repeatedly attempted to ascertain whether perivascu- 

 lar nerves were to be found on the vessels of the choroid plexus 

 in the lateral ventricles. My results have thus far, however, been 

 negative. This, I believe, is in part at least due to the fact that 

 in methylen blue preparations — both when the methylen blue 

 is injected into the circulation and when applied in very dilute 

 solution (i to 1000 in normal salt solution) to the fresh cho- 

 roid plexus — the epithelial cells covering the vessels of the 

 choroid plexus stained so deeply that the underlying structures 

 could not be made out with any degree of clearness. 



As to the nerves in the pia-mater of the cerebellum, my 

 results have not been so conclusive as might be desired. 

 Sensory nerves have now and then been traced by the side of 

 the arteries of the pia-mater of the cerebellum ; these end as 

 do similar nerves in the pia-mater of the cerebral hemispheres. 

 Vaso-motor nerves have been met with in only a few cases, and 

 then only in small numbers and not so clearly stained as in 

 other parts of the pia. 



Nerves of the Dura-mater. The presence of nerves in the 

 dura-mater seems beyond question. Their origin, course and 

 to some extent distribution have been known to anatomists for 

 many years. It is not my purpose at this time to concern 

 myself with these grosser anatomic facts, as my observations 

 have not been of a nature to give me data for this purpose. In 

 a number of experiments on dogs, cats and rabbits, I have 



